Hyderabad: A possible design fault that did not factor in the shifting of sand from under the foundations of the Lakshmi barrage at Medigadda on the Godavari river is believed to be the primary cause for the subsidence of one of the seven blocks of the barrage, making the structure useless with respect to the storage of water.
For all practical purposes, Medigadda Barrage for the next few years would be a structure without a Barrage use as it can no longer hold any water – let alone the 16 thousand million cubic feet (tmc ft) it is supposed to store.
“What we are seeing is a barrage which can no longer serve the purpose it was designed and built for,” authoritative sources told Deccan Chronicle. This was also corroborated by the irrigation department which said until the actual problem is identified – which could take a while – and rectification is done, if at all that is possible, the barrage will no longer be able to store any water.
On Tuesday, a six-member team deputed by the National Dam Safety Authority to inspect the barrage and the damage visited Medigadda, accompanied by irrigation department officials and engineers from L&T Construction which built the barrage. The team was deputed following a complaint from Union Minister and state BJP president G. Kishan Reddy to the Union water resources ministry.
Irrigation department sources added that water resources were bad. “The barrage is built in blocks, and only one of the seven blocks is affected. In a worst-case scenario, the block may have to be rebuilt from the ground up. The rest of the structure is safe,” the sources maintained.
One of the explanations that has come forth from the irrigation department, at least for now, is that the most likely problem for the sinking of Block 7 was the shifting of sand from under the foundations due to the river water’s pressure and force.
This raises even more uncomfortable questions about the design and approvals by the irrigation department of the construction process. “If the foundation was anchored in sheet rock, then there should be no impact if sand shifts due to sheet rock flow, or sudden flood,” the sources said.
They said there were some concerns raised over the design of the pillars and foundations by one side during the construction, but this aspect could not be independently verified. The sources said even if the shifting of the sand was an issue, this possibility should have been factored in while finalising the design.
L&T Construction which built the barrage as per designs and specifications provided by the irrigation department is learnt to have employed what is called a ‘secant’ foundation system — a hybrid model of piles driven into the sheet rock through a lattice kind of a network of a raft foundation which typically is an extended foundation designed to bear the load of a structure.
For now, there is the normal flow of water in the Pranahita River, which is allowed to flow freely. The barrage was designed to store 16 tmc ft of water (16 times the water that is held in the Hussainsagar). It could have been the flood last year when 28.7 lakh cusecs (cubic feet per second) of water from the Pranahita and Godavari buffeted the barrage which was designed to withstand 28.25 lakh cusecs of flow.
It was this flood and the backwash from it that also submerged the Lakshmi pump house near the same barrage, raising questions about the project’s safety.
